(a) Field of the Invention
The present invention relates to a display device, and a method of driving the display device.
(b) Discussion of Related Art
In designing personal computers and televisions having light-weight and reduced form factor, display devices are needed having light-weight and flat profiles. To satisfy such needs, cathode ray tubes (CRTs) have been replaced by flat panel display devices.
A flat panel display device may be a liquid crystal display (LCD), a field emission display (FED), an organic light emitting display, a plasma display panel (PDP), etc.
Typically, flat panel display devices include a plurality of pixels arranged in the form of a matrix, and the light intensity at each pixel is controlled depending upon given luminance information. The organic light emitting display electrically excites luminescent organic material, and emits light to display the desired images. The organic light emitting display characteristics include self-light emission, lower power consumption, wide viewing angle and short response time. The organic light emitting display may display high quality moving picture images.
The organic light emitting display includes organic light emitting diodes (OLEDs), and thin film transistors (TFTs) for driving the OLEDs. The TFTs are classified into a polycrystalline silicon TFT and an amorphous silicon TFT depending upon a type of active layer. The organic light emitting display using the polycrystalline silicon TFTs exhibits various advantages, and has been extensively used. However, manufacture of the organic light emitting display using the polycrystalline silicon TFTs involves complicated processing steps and increased production cost, and it can be difficult to obtain a wide screen with such an organic light emitting display.
A wide screen can more easily be manufactured in an organic light emitting display implementing the amorphous silicon TFT, which involves simplified processing steps compared to the organic light emitting display using the polycrystalline silicon TFT. In the organic light emitting display using the amorphous silicon TFT, a threshold voltage Vth shifts and deteriorates as an electric current is continuously applied to the OLED. As a result, an uneven electric current flows through the OLED even under the application of the same data voltage. For this reason, the display quality of the organic light emitting display using the amorphous silicon TFT is deteriorated.
Therefore, a need exists for a display device that has amorphous silicon thin film transistors and substantially prevents the deterioration of the threshold voltage thereof, and a method of driving the display device.